As a conventional mixer, there is a stub branching mixer using an anti-parallel diode pair (APDP). The mixer is a mixer to which a radio frequency (RF) signal and a local oscillator frequency (LO) signal are input, and which extracts a component of (RF signal frequency−2×LO signal frequency) with the use of diodes connected in anti-parallel to each other (for example, refer to Non-patent Documents 1 and 2).
Further, a general mixer using an open stub and a short stub is disclosed (for example, refer to Patent Documents 1 and 2). Further, as a line transducer used for the mixer, there is disclosed a waveguide/microstrip line transducer having a configuration in which a conductor is connected to a ground plane of a waveguide (for example, refer to Patent Documents 3 and 4). Further, there is disclosed a configuration in which a resistor that divides a voltage applied to the APDP is provided to thereby increase a ratio of an output power when the RF signal is on, and an output power when the RF signal is off (for example, refer to Patent Document 5).    Non-patent Document 1: “8.4.2 Microstrip SHP Mixer”, Microwave Mixers Second Edition, Stephen A. Maas, p. 311    Non-patent Document 2: The Institute of Electronics, Information and Communication Engineers “Monolithic Microwave Integrated Circuit (MMIC)” pp. 120-122    Patent Document 1: JP 2980033 B    Patent Document 2: JP 3147852 B    Patent Document 3: JP 3672241 B    Patent Document 4: JP 3828438 B    Patent Document 5: WO 2005/043744 A1